Code 128

Code 128 is a high-density 1D symbology covering the full ASCII range. pyStrich automatically switches between code sets A, B and C to minimise symbol length, and computes the mod-103 checksum for you.

See also

Code 128 on Wikipedia for background on the symbology itself.

Example

from pystrich.code128 import Code128Encoder

encoder = Code128Encoder("WDBCA45D2HA327260")
encoder.save_svg("code128-example.svg")

Sizing, label, font and layout

The bar_width argument to save() and get_imagedata() sets the pixel width of the narrowest bar (default 3).

The options dict passed to Code128Encoder controls the human-readable label and the surrounding layout. All keys are optional.

show_label

Whether to render the human-readable label underneath the bars. Defaults to True; set to False to suppress it.

ttf_font

Absolute path to a TrueType font file used for the label. Defaults to a bundled bitmap font if unset.

ttf_fontsize

Font size in points.

height

Total image height in pixels. Defaults to roughly a third of the image width.

label_border

Pixels of vertical space between the bars and the label.

bottom_border

Pixels of vertical space between the label and the bottom edge.

See also

Printing barcodes for guidance on selecting bar_width for printed output.

options = {
    "height": 200,
    "label_border": 10,
    "bottom_border": 10,
    "ttf_fontsize": 24,
    # "ttf_font": "/usr/share/fonts/truetype/dejavu/DejaVuSans.ttf",
}
encoder = Code128Encoder("WDBCA45D2HA327260", options=options)
encoder.save("code128-custom.png", bar_width=4)

Output formats

SVG output

For embedding in web pages or any workflow that benefits from resolution-independent output, use save_svg() (or get_svg() to receive the SVG as a string).

Code128Encoder("WDBCA45D2HA327260").save_svg("code128.svg")

The SVG’s viewBox is in module units (one narrow bar = one unit), while width and height scale by bar_width. The 10-module quiet zones mandated by the standard are applied automatically on each side.

Added in version 0.12.

PNG output

For raster output, use save() to write a PNG file or get_imagedata() to receive the raw PNG bytes.

Code128Encoder("WDBCA45D2HA327260").save("code128.png")

EPS output

For embedding in LaTeX (\includegraphics) or other vector print workflows, use save_eps() (or get_eps() to receive the EPS as a string).

Code128Encoder("WDBCA45D2HA327260").save_eps("code128.eps")

The bar_width argument is the width of the narrowest bar in PostScript points (1 point = 1/72 inch). The 10-module quiet zones are applied automatically.

Added in version 0.12.

API

class Code128Encoder(text: str, options: BarcodeRenderOptions | None = None)

Bases: Bar1DEncoder

Encode a string as a Code 128 1D barcode.

Code sets A, B and C are switched between automatically to minimise symbol length. The mod-103 checksum is computed and appended for you.

Typical use:

encoder = Code128Encoder("nm0000385")
encoder.save("barcode.png")

Variables:

• text – The original input text.

• encoded_text – List of code values produced by the text encoder, including start codes and code-set switches.

• checksum – The mod-103 checksum value.

• bars – The bar/space pattern as a string of "1" and "0".

• options – Render-time options dict (empty if none were supplied).

• width – Pixel width of the most recently rendered image. 0 until a render method has been called.

• height – Pixel height of the most recently rendered image.

get_eps(bar_width: int = 3) → str

Render the barcode and return EPS markup.

Parameters:

bar_width – Width in PostScript points of the narrowest bar.

Return type:

str

Added in version 0.12.

get_imagedata(bar_width: int = 3) → bytes

Render the barcode and return PNG bytes.

Parameters:

bar_width – Width in pixels of the narrowest bar.

Returns:

PNG-encoded image data.

Return type:

bytes

get_pilimage(bar_width: int = 3) → PIL.Image.Image

Render the barcode and return a Pillow image.

Parameters:

bar_width – Width in pixels of the narrowest bar.

Returns:

The rendered barcode.

Return type:

PIL.Image.Image

Added in version 0.11.

get_svg(bar_width: int = 3) → str

Render the barcode and return SVG markup.

Parameters:

bar_width – Width in user units of the narrowest bar.

Return type:

str

Added in version 0.12.

save(filename: str | PathLike[str], bar_width: int = 3) → None

Render the barcode to a PNG file.

Parameters:

• filename – Path to write the PNG to.

• bar_width – Width in pixels of the narrowest bar.

save_eps(filename: str | PathLike[str], bar_width: int = 3) → None

Save the barcode as an EPS file. Pass an .eps filename.

Parameters:

• filename – EPS output path.

• bar_width – Width in PostScript points of the narrowest bar.

Added in version 0.12.

save_svg(filename: str | PathLike[str], bar_width: int = 3) → None

Save the barcode as an SVG file. Pass a .svg filename.

Parameters:

• filename – SVG output path.

• bar_width – Width in user units of the narrowest bar.

Added in version 0.12.

calculate_check_sum() → int

Compute the Code 128 mod-103 checksum for encoded_text.

The start code contributes with weight 1; subsequent symbols are weighted by their 1-based position before the modulo is taken.

init_renderer() → Code128Renderer

Construct a Code128Renderer for the encoded bars.

Return type:

Code128Renderer